The present invention relates generally to a device for testing magnetic properties of coins in coin-operated apparatus, particularly for setting and displaying the parking time in a parking meter. The device is used in conjunction with a coin diameter testing device for testing the diameter of a coin which temporarily rests on a coin support of the device.
Experience has shown that in coin-operated apparatus, such as parking meters, it is no longer sufficient to restrict the test of a coin to the test of its diameter in order to determine the genuineness of the coin. In coin-operated apparatus, such as parking meters, it is frequently attempted to operate the apparatus in an unauthorized manner by inserting objects resembling coins, such as disks, plastic chips or the like. This unauthorized use is possible when the diameter of a counterfeit coin corresponds with sufficient accuracy to the dimensions of a genuine coin and if, moreover, no other properties in addition to the diameter of the coin are tested.
An effective test of the genuineness of a coin becomes difficult when the counterfeit coins are so-called gambling money of plastics material whose outer dimensions and in both surfaces are fashioned exactly as the metal coins which are circulating as genuine legal tender. To be able to distinguish such plastic coins from genuine metals coins of the same type, it is possible to utilize the behavior of iron-containing metal coins with respect to the force of a magnetic field.
Another possibility would be to classify the coins with respect to their differing weights and to guide them into appropriate coin ducts. In accordance with this method, a sensitive coin scale is used and, in addition, a long coin conveying path is required, into which path the coin scale is indicated and in which acceptable and unacceptable coins are conducted through two separate ducts.
The utilization of coin scales in parking meters has not proved defective because of the hostile environmental conditions to which parking meters are subjected. It has been found that a solution by weighing does not ensure a satisfactory operation. The influences to which a coin scale in a parking meter are subjected can be explained by the location of parking meters. As a rule, parking meters are located at the curb of a road or other outdoor site where extreme conditions such as cold temperatures, moisture, and dirt have detrimental effects on the sensitive components of a coin scale.
In view of the above, coin testing devices have become known which classify the coins to be tested on the basis of a magnetic field interacting with the iron content of the coin material, which then divert them into transport ducts or generally refuse acceptance or the like.
German Utility Model No. 17 45 460 describes a simple magnetic coin test wherein a magnet is provided in a coin duct which magnet diverts a coin into a specific direction due to the influence of a field of magnetic force. In accordance with the utility model, a permanent magnet in the shape of a circular disk is magnetized in such a way that the lines of magnetic force extend externally approximately around each half of the disk. A coin which can be magnetically influenced falls due to its own weight through the zone of field lines of the magnetic disk and rolls with its outer surface on the magnetic disk as a result of the attraction forces acting on it. A genuine coin is deflected into a coin duct which, in conjunction with a diameter test, serves to trigger the operation of the parking meter. A coin which cannot be influenced magnetically, on the other hand, falls through vertically without any deflection by the magnetic disk into a collecting container.
The efficiency of the magnetic field through the opposing circular arc-shaped surfaces upon the coin is very poor because the two surfaces theoretically contact one another only along the short line corresponding to the thickness of the coin. Moreover, this device operates only in one mode of operation, that is, only coins containing iron are accepted as genuine coins because only ferromagnetic coins can reach the coin duct for utilizable coins. All coins of non-ferrous material or plastic chips fall through vertically, past the diameter testing station, into a special duct and a collecting container. This also means that two separate coin conveying ducts corresponding to genuine and counterfeit coins must be provided.
German Offenlegungsschrift No. 22 43 221 disclosed another magnetic coin testing apparatus, wherein a rotatably mounted locking bolt blocks in its position of rest with its one end a sensor pin at a double lever for sensing the diameter and releasing the time, and extends with its other end which carries a magnet into the coin conveying path. The magnet test lever interacts in principle directly with a pivotable diameter sensing member by means of a swing arm, so that a diameter sensing element or sensor pin and, thus, the double lever, is held in a locking position. The magnetic arm of the locking lever precedes the diameter test and extends into the coin insertion duct. Only if a ferromagnetic coin is inserted is the locking lever arm moved during the transport of the coin due to the attraction forces between the coin and the magnetic locking lever arm, and the latter, as the effective sensing member, releases the sensor pin for the diameter test. The diameter testing member is part of a double lever which, in turn, locks or releases the sensing member for setting a time control device. If a time setting is to be triggered, the double lever must be released before any diameter test is performed. This release can only occur by means of an object containing iron.
The transport of the locking lever effected solely by the field of magnetic force does not ensure an absolutely safe operation. The conditions of friction between the locking lever and the double lever lead to many operational uncertainties. The elimination of a ferromagnetic coin from non-ferrous coins can be accomplished with this apparatus because the double lever can be controlled by the locking lever for releasing the time setting only by means of coins of ferromagnetic materials.
In accordance with the coin testing device known from the German Pat. No. 24 45 204, a testing zone whose cross-sectional area is expanded is provided in the coin conveying duct. Two magnets are arranged on the same level at a fixed coin duct wall which attract those passing coins which can be magnetically influenced. A spring-loaded sensor lever which extends into the testing zone is deflected into a position releasing the time setting means of a lateral movement of the coin.
The testing device discussed above is only capable of recognize ferromagnetic coins as acceptable, because only these coins actuate a time release. The reverse case, i.e., the recognition in the testing zone of non-ferrous coins as acceptable, cannot be achieved with this known solution. A further disadvantage resides in the fact that the coin which is attracted through magnetic force across an air gap, must overcome the spring force of the sensor lever and additional frictional resistance in order to achieve a time release.
Finally, German Offenlegungsschrift No. 29 49 658 describes a coin testing device for parking meters with a coin conveying system. In this device, the cross-sectional area of the coin conveying duct is expanded as compared to the thickness of an acceptable coin. Also, stationary magnets are provided in a side wall which magnets cause a lateral shift of the passing ferromagnetic coin. In order to distinguish between coins of equal diameter, coin support paths are provided in the region of the testing zone, which paths are offset laterally and arranged at different levels with respect to the support base. A coin which can be influenced by a magnet is laterally deflected by the force of the magnet and reaches the corresponding coin support base which differs in level from the coin support base for coins containing no iron. With respect to coins having equal diameters, the deflection to the different support bases in the testing zone simulates the presence of coins having different diameters in order to enable a selection. This device is actually only suitable for differentiating between coins which have equal diameters, but which are of magnetically different materials. In addition, the coins are conducted by means of a conveying system positively through the testing zone.
It is the object of the present invention to provide a simple device for testing the magnetic properties of coins which have been inserted into a coin testing unit of a coin-operated apparatus and for further triggering the acceptance of usable coins or the collection of counterfeit coins.